Glass grinding method and apparatus



Jan. ll, 1955 E. LAvERDlssl-z 2,699,021

GLASS GRINDING METHOD AND APPARATUS Filed March 16, 1953 2 Sheets-Sheet 1 E. LAVERDISSE GLASS GRINDING METHOD AND APPARATUS Jan. 11, 1955 2 Sheets-Sheet 2 Filed March 16, -1953v United States Patent O GLASS GRHNDING METHOD AND APPARATUS Edmond Laverdisse, Auvelais, Belgium, assgnor to Les Glaceries de la Sambre Societe Anonyme, Auvelais, Belgium, a Belgian company Application March 16, 1953, Serial No. 342,350

Ciaims priority, application Belgium March 20, 1952 14 Claims. (Cl. 51--209) The present invention relates to the feeding of abrasive composition to the irons, that is to say, to the discoidal tools employed for grinding rough glass. The abrasive generally employed consists of a mixture of hard sand and water and is generally introduced to the centre of the tool through a duct formed in the shaft by which the latter is driven.

When the two faces of the glass sheet must be simultaneously ground, the upper tool is fed by gravity, while the lower tool receives the abrasive under a hydrostatic pressure sufficiently high to cause it to penetrate between the glass and the working surface of the tool which is preferably divided into shoes, for example by radial and circular grooves. However, this method of feeding the lower tools has the disadvantage of necessitating a relatively high pressure which tends to cause on the one hand lifting and deformation of the glass sheet at the point at which the abrasive under pressure arrives, with danger of fracture, and on the other hand irregularities in the distribution and discharge of the abrasive.

It is also known to feed the tools with abrasive under the action of centrifugal force, from the centre to the periphery of the tool, by feeding the abrasive into the central part of the tool.

This centrifugal feeding method, however, is relatively complicated and uncertain and involves soiling.

The present invention has for its object to obviate all these disadvantages and to provide a simple and effective method of and means for feeding and equally distributing the abrasive during the grinding. Although the said means are not limited to this application, they are particularly suitable for tools of small diameter such as those rrllounted in juxtaposition in a beam of a grinding mac me.

The essential feature of the present invention resides in that the abrasive introduced into the interior of the tool is directed therein from a central point relatively distant from the Working plane of the shoes, in the direction of the said plane, along an inclined path progressively approaching the working surface of the first ring of shoes.

In adidtion, in accordance with the invention, the abrasive is advantageously guided along the inclined path so as to be prevented from coming into contact with the glass sheet in the central zone of the tool.

In accordance with a further feature of the invention, the abrasive brought to the centre of the tool is subjected at this point to a centrifugal impulse variable independently of the rotation of the tool.

In a tool constructed in accordance with the invention7 there is disposed immediately around the mouth through which the abrasive is transferred into the central cavity of the tool a centrifugal bladed impeller which takes up the abrasive and forces it towards the periphery while distributing it equally in all directions, and in order to promote the formation and spreading of a layer of abrasive, and the penetration thereof between the surface of the glass and the friction surfaces of the shoes formed between the grooves, the central cavity of the tool comprises a dished portion the depth of which is greatest at the centre and decreases progressively towards the periphery, the said cavity opening towards the working plane of the tool and being provided with blades constituting a centrifugal impeller and abrasive distributor, while the mouth of the duct through which the abrasive is fed opens into the deepest part of the said cavity.

The grooves separating the shoes of the tool from 2,699,021 Patented Jan. 1l, 1955 ICC one another may be provided with oblique or inwardly curved edges to facilitate the penetration of the abrasive under the action of centrifugal force.

In tools of small dimensions which are adapted to rotate at great speed, the blades of the impeller are xed or formed directly on the wall of the dished portion. In large tools, the angular velocity of which is limited, the impeller constitutes an independent member actuated at higher speed. In both cases, the arrangement is such that the abrasive mixture is taken up by the blades as soon as it leaves the axial duct and enters the dished portion.

In some cases the central feed may be combined with a feed at other points of the tool.

Two embodiments of the invention are diagrammatically illustrated by way of example in the accompanying drawings in which:

Figure 1 is a diametral vertical section on the line I-I of Figures 2 and 3 through a pair of tools acting simultaneously on the two faces of a glass sheet,

Figures 2 and 3 are plan views of the lower tool as seen from above and of the upper tool as seen from below,

Figure 4 is a vertical diametral section showing a pair of tools provided with separate impellers,

Figure 5 is a diametral section along the line V-V of Figures 6 and 7 through a pair of tools having double feed, and

Figures 6 and 7 are horizontal sections along the lines VI-VI and VII-VII respectively of Figure 5 In the drawings, 1 and 1 are the lower and upper tools respectively, which are mounted on the shafts 2, 2 rotated by the gears 3, 3'. The shafts 2, 2 are hollow and have extending therethrough fixed tubes 4, 4, one of which conducts to the lower tool the abrasive supplied under a low pressure by a pump 5, for example, while the other conducts to the upper tool the abrasive coming from a gravity-feed container (not shown).

The duct 4 by which the lower tool 1 is fed opens into a central cavity 6 in the latter, the cavity 6 having the form of a conical dished portion in the example illustrated in Figures l to 3. The abrasive iiowing over the flange 7 surrounding the mouth of the tube 4 falls on to ribs or blades 8 which are provided on the base of the conical cavity 6 and guide the abrasive to the surface of the tool, while distributing it equally in all directions. If the tools are of small diameter, as in the case of tools mounted in line on a beam, the diameter of which is generally of the order of 50 to 60 cm., they may be actuated with a rapid rotation reaching, for example, 500 to 600 R. P. M., without reaching an excessive peripheral velocity. Under these conditions, the action of centrifugal force begins to take effect very close to the centre and the abrasive is projected by the blades 8 upwardly and outwardly. If it is desired to prevent abrasive from being projected into the inactive central zone of the tool, the ribs 8 may be covered by a cap, for example of conical form.

An important advantage of this arrangement resides in the equal distribution of the abrasive impelled by the blades, which permits of avoiding an excessive alux of abrasive towards the parts of the tool which are uncovered by the edge of the glass in the course of the operation and thus create zones in which the resistance to the passage of the abrasive is reduced to the detriment of the mrking parts of the tool, which are then inadequately The body of the tool 1 is divided into friction shoes 9 by circular grooves 10 and radial grooves 11 which intersect, and wherein the shoes of each circular row are preferably staggered circumferentially with respect to the shoes in the adjacent rows. Preferably, the outer faces of the grooves 10 are inclined to promote the progress of the abrasive and to bring it constantly towards the surface of the tool in contact with the glass. The inclination of these faces may be constant or variable, the faces 12 then being curved as indicated in Figure l.

The arrangement of the upper tool l is generally similar to that of the lower tool, those elements which correspond to the elements hereinbefore described being designated by the same reference numerals provided with the index The abrasive fed through the xed duct 4 here falls on to a cone 13 covering the blades 8' connected to the dished portion, which project the abrasive outwardly. The action of the centrifugal force is exerted as in the lower tool.

When the angular velocity of the tool is insufficient for the action of the centrifugal force to take effect immediately the abrasive arrives in the central cavity 6 or 6, the impeller is formed by an independent element mounted on a rotative sleeve concentric to the axis 2 or 2 and actuated by a step-up transmission gear at an angular velocity higher than that of the tool. The invention is thus rendered applicable to tools whose large dimensions do not permit of adopting high angular velocities.

Figure 4 shows an arrangement of this nature in which the lower tool is provided with a bladed impeller 14 and has a conical base 15 mounted on a sleeve 16, the rotation of which is controlled by the shaft 25 through step-up gears 17. The abrasive flowing over the flange 7 falls on to the conical surface 15, whence it is projected towards the outside of the cavity 6 by the blades 14.

Similarly, the upper tool comprises a bladed impeller 14 and a conical base 15 fast with the sleeve 16 actuated by the step-up gears 17. The abrasive fed through the tube 4 passes through the peripheral holes 18 in the base of the tube and falls on to the cone 15 of the impeller, the blades of which force it towards the outside.

In the embodiment of the invention as illustrated in Figures to 7, the feed is divided so that only a part of the abrasive is fed to the centre, the remainder being fed to points closer to the periphery of the tool.

For this purpose, in the lower tool the feed duct 4 has formed therein lateral orifices 19, through which the abrasive passes, the said abrasive falling from the overflow edge 20 on to the plate 21 forming the base of the tool with which it turns. The centrifugal force impels the said abrasive through the radial ducts 22, which open into slots 23 at the base of circular grooves 10 more or less distant from the centre according to requirements.

The orifices 19 are so calibrated as to permit the passage of only a limited quantity of abrasive, the remainder being fed through radial nozzles 24 directed along the conical base of the cavity 6, whence the abrasive falls between the blades 8, which impel it in the manner hereinbefore described.

In the upper tool, the abrasive fed through the tube 4 is distributed between the peripheral orifices 26 from which it falls over the overow 20 on to the rotating plate 21 formed with radial ducts 22', and the calibrated orifice 27, from which it falls on to the cone 13 which, with the blades 8', constitutes the impeller.

It is obvious that a triple feed is possible instead of the double feed hereinbefore described and that other modifications may be made to the examples described without departing from the scope of the invention. In all these cases, the action of the judiciously applied centrifugal force prevents the application of a high hydrostatic pressure on the glass at the point of the central cavity of the tool and thus obviates the danger of bending and fracture of the sheet. Moreover, the construction of the tool is simple and ensures reliable and effective operation.

I claim:

l. In apparatus for grinding the surfaces of a sheet of glass, a rotary grinding tool comprising endless rows of shoes arranged in radially spaced apart relationship, the shoes in each of said rows being spaced apart in the direction along the related row, a hollow tool driving spindle, a duct arranged coaxially within the tool driving spindle, a dished portion at the centre of the tool, the depth of said dished portion diminishing progressively from the centre to the periphery of the latter, centrifugal irnpeller means arranged within said dished portion, means for rotating said tool, low pressure means supplying abrasive through the duct and the centrifugal impeller to the shoes and a sloping face on each shoe directed from the centre of rotation towards the grinding surface of the tool.

2. In apparatus for grinding the surfaces of a sheet of glass, a rotary grinding tool according to claim l, wherein the centrifugal impeller means includes a plurality of irnpeller blades, a base, the depth of which progressively diminishes from the centre towards the periphery, disposed within the dished portion and having the blades mounted thereon, a sleeve mounted coaxially within the spindle of the tool and externally of the duct, said base being fixed to the inward end of said sleeve, and gear means for rotating said sleeve and base bearing the impeller blaies at a speed greater than the speed of rotation of the too 3. In apparatus for grinding the surfaces of a sheet of glass, a rotary grinding tool according to claim 1, wherein the centrifugal impeller means includes a plurality of impeller blades mounted in the dished portion of the tool.

4. In apparatus for grinding the surfaces of a sheet of glass, a rotary grinding tool according to claim 1, including a cap disposed between said impeller means and the working plane of the tool.

5. In apparatus for grinding the surfaces of a sheet of glass, a rotary grinding tool according to ciaini l, wherein the impeller means includes radially extending impeller blades and a plurality of nozzles connected to the duct and disposed substantially parallel to the surface of the dished portion to discharge abrasive between said blades.

6. In apparatus for grinding the surface of a sheet of glass, a rotary grinding tool comprising a body portion, series of shoes on said body portion spaced apart in the radial direction and in the direction around said body portion, each of said shoes being disposed radialiy opposite the spaces between the next adjacent radially inner and outer shoes, a hollow tool-driving spindle, a duct coaxially mounted within the hollow spindle, means at the end of said duct adjacent the tool directing a flow of abrasive axially and radially towards the shoes, said body portion formed with radial ducts conducting the radially directed abrasive to the shoes near the periphery of the tool, a dished portion at the centre of rotation of thc tool the depth of said dished portion diminishing progressively from the centre towards the periphery of the latter and a centrifugal impeller within said dished portion.

7. In apparatus for grinding the surfaces ef a sheet of glass, a rotary grinding tool according to claim 6, wherein the centrifugal impeller comprises a plurality of impeller blades, a base, the depth of which progressively diminishes from the centre towards the periphery, disposed within the dished portion and having the blades mounted thereon, a sleeve mounted coaxially within the spindle of the tool and externally of the duct, said base being xed to the inward end of said sleeve, and gear means for rotating said sleeve and impeller at a speed greater than the speed of rotation of the tool.

8. In apparatus for grinding the surfaces of a sheet of glass, a rotary grinding tool according to claim 6, wherein the centrifugal impeller comprises a plurality of mreller blades mounted in the dished portion of the 9. In apparatus for grinding the surfaces of a sheet of glass, a rotary grinding tool according to claim 6, including a cap disposed between said impeller and the working plane of the tool.

l0. In apparatus for grinding the surfaces of a sheet of glass, a rotary grinding tool according to claim 6, wherein theimpeller comprises angularly spaced blades and a plurality of nozzles connected to the duct and disposed substantially parallel to the surface of the dished portion to discharge abrasive between said blades.

11. A process for grinding the surfaces of a sheet of glass, which comprises, feeding abrasive to a centrifugal impeller arranged centrally of a rotary grinding tool, while rotating said tool and said impeller, the centrifugal action of said impeller causing said abrasive to be displaced radially towards a plurality of shoes comprising the working surface of the grinding tool, the centrifugal action of the tool causing said abrasive to mount along outwardly sloping faces of the shoes to the working surfaces thereof.

12. A process according to claim 1l, characterised in that the rotational speed of the centrifugal impeller is greater than that of the tool.

13. A process for grinding the surfaces of a sheet of glass, which comprises feeding abrasive to a rotary grinding tool by means of a duct arranged coaxially within the spindle of said tool, causing the abrasive to [low radially and axially from said duct, directing the radial flow of abrasive through the body of the tool to a plurality of shoes near the periphery of the tool and the axial flow of abrasive t0 a centrifugal impeller and from said impeller to a plurality of shoes near the centre of rotation of said tool.

14. A process according to claim 13, characterised 5 6 in that the rotational speed of the centrifugal impeller is 1,856,173 Stahle May 3, 1932 greater than that of the tool. 1,924,597 Drake Aug. 29, 1933 2,179,740 Grin Nov. 14, 1939 References Cited in the flle of this patent 2,264,177 Harrington Nov. 25, 1941 UNITED STATES PATENTS 696,195 Rogers Mar. 25, 1902 

